/Engine/Source/Editor/UnrealEd/Public/FileHelpers.h
Looks at all currently loaded packages and saves them if their "bDirty" flag is set, optionally prompting the user to select which packages to save)
true on success, false on fail.
static bool SaveDirtyPackages ( const bool bPromptUserToSave, const bool bSaveMapPackages, const bool bSaveContentPackages, const bool bFastSave, const bool bNotifyNoPackagesSaved, const bool bCanBeDeclined, bool * bOutPackagesNeededSaving, const [FShouldIgnorePackageFunctionRef](API\Editor\UnrealEd\FEditorFileUtils\FShouldIgnorePackageFunctionRef) & ShouldIgnorePackageFunction )